Built-in variables and functions

Besides the material's properties, shader code can read the values Unity provides every frame, such as the time and the camera, and call three libraries of functions.

Built-in variables

The variables are properties of the shader's base class, so shader code uses them directly by name.

Time

Variable	Value
Time	Time since the level loaded, in seconds: (t / 20, t, t * 2, t * 3). Time.y is the time itself.
SinTime	(sin(t / 8), sin(t / 4), sin(t / 2), sin(t)).
CosTime	(cos(t / 8), cos(t / 4), cos(t / 2), cos(t)).
TimeParameters	(t, sin(t), cos(t), dt).
unity_DeltaTime	(dt, 1 / dt, smoothed dt, 1 / smoothed dt).

// Scrolls the texture by half a UV unit per second.
float2 uv = BaseMap.GetTransformedUV(IN.uv0) + new float2(Time.y * 0.5f, 0);

Camera and screen

Variable	Value
WorldSpaceCameraPos	The camera's position in world space.
ProjectionParams	x: 1, or -1 with a flipped projection; y: near plane; z: far plane; w: 1 / far plane.
ScreenParams	The render target size: x width and y height in pixels.
ZBufferParams	Parameters for converting depth to linear depth; usually you use ShaderApi.LinearEyeDepth instead.
unity_OrthoParams	Orthographic camera size; w is 1 for an orthographic camera, 0 for a perspective one.

Important

On HDRP, WorldSpaceCameraPos is an absolute position while IN.positionWS is relative to the camera, so don't subtract one from the other. For the direction to the camera, use ShaderApi.GetWorldSpaceViewDir or ShaderApi.GetWorldSpaceNormalizeViewDir, which work on both pipelines.

Object

Variable	Value
unity_LODFade	LOD Group cross-fade progress, in x.
unity_WorldTransformParams	w is -1 when the object is mirrored by a negative scale.
unity_RenderingLayer	The renderer's rendering layer mask.
unity_LightmapST, unity_DynamicLightmapST	How the object's lightmap UVs map into the baked and realtime lightmaps.
unity_SHAr … unity_SHC	The ambient lighting, as spherical harmonics coefficients.

URP-only variables

ScaledScreenParams, the matrices unity_ObjectToWorld, unity_WorldToObject, unity_PrevObjectToWorld, unity_PrevWorldToObject, unity_MatrixV, unity_MatrixVP, glstate_matrix_projection, unity_CameraProjection and unity_CameraInvProjection exist on URP only. Using them makes the shader fail to compile on HDRP. For code that works on both pipelines, use the ShaderApi transform functions instead, such as ShaderApi.TransformObjectToWorld or ShaderApi.TransformWorldToHClip.

ShaderApi

ShaderApi holds functions from Unity's render pipeline shader libraries. They work the same on URP and HDRP, unless noted otherwise.

Group	Functions
Space transforms	TransformObjectToWorld, TransformWorldToObject, TransformObjectToWorldNormal, TransformObjectToWorldDir, TransformWorldToView, TransformWorldToHClip and the other directions; GetAbsolutePositionWS, GetCameraRelativePositionWS
View direction	GetWorldSpaceViewDir, GetWorldSpaceNormalizeViewDir, GetObjectSpaceNormalizeViewDir
Normals and tangent space	UnpackNormal, UnpackNormalScale, UnpackNormalRGB, BlendNormalRNM, CreateTangentToWorld, TransformTangentToWorld, TransformObjectToTangent
Depth	LinearEyeDepth, Linear01Depth
Screen	GetNormalizedScreenSpaceUV; SampleSceneColor, SampleSceneDepth: the scene behind a transparent object (see The screen)
Parallax	GetViewDirectionTangentSpace, ParallaxOffset1Step, ClampNdotV
Object	GetObjectScale, GetObjectScaleInverse, GetOddNegativeScale
Environment	GetAmbientSkyColor, GetAmbientEquatorColor, GetAmbientGroundColor, GetFog; on HDRP these return 0, like Shader Graph's Ambient and Fog nodes
Pixel control	clip, which discards the pixel when its argument is negative
Screen-space derivatives	ddx, ddy, fwidth: how fast a value changes between neighboring pixels; Frag only

// A rim of light where the surface turns away from the camera.
float3 viewDir = ShaderApi.GetWorldSpaceNormalizeViewDir(IN.positionWS);
float rim = 1 - math.saturate(math.dot(math.normalize(IN.normalWS), viewDir));

ShaderLib

ShaderLib is a library of ready-made shader functions. Many of them produce the same result as Shader Graph nodes of the same name, so an effect made in Shader Graph can be rebuilt in code.

Group	Functions
Noise	GradientNoise, SimpleNoise, Voronoi
Shapes	Ellipse, Rectangle, RoundedRectangle, Polygon, RoundedPolygon, Checkerboard; Frag only
UV	TilingAndOffset, RotateRadians, RotateDegrees, Twirl, Spherize, PolarCoordinates, RadialShear, Flipbook
Utility	Remap, Posterize, RandomRange, FresnelEffect, Dither
Lighting units	Ev100ToNits, NitsToEv100, ApplyExposureWeight

// A dissolve effect: noise decides which pixels disappear first.
float noise = ShaderLib.SimpleNoise(uv, 20);
ShaderApi.clip(noise - DissolveAmount);

math

math holds the HLSL math functions and constants: sin, lerp, smoothstep, saturate, dot, normalize, mul and the rest, plus constants like math.PI. They are described with the language in Math.